Method of minitoring status information of remote storage and storage subsystem

ABSTRACT

A host computer acquires remote copy status information of storage subsystems that are not directly coupled to the host computer. Each storage subsystem comprises: a unit which receives a status information acquisition command from the host computer; a unit which analyses the received command to judge whether the storage subsystem in question is a target of the command; a unit which sends the command to a downstream storage subsystem connected to the storage subsystem in question when the storage subsystem in question is not the target; and a unit which sends status information to an upstream storage subsystem connected to the storage subsystem in question when the status information is received from the downstream storage subsystem.

The present application is a continuation of application Ser. No.10/788,453, filed Mar. 1, 2004, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a storage subsystem and a technique ofcontrolling a storage subsystem, and in particular, to a technique ofcollecting status information etc., of a storage subsystem that isplaced, for example, in a remote place and not directly coupled to ahost computer.

As information-oriented society develops, computer systems areintroduced all over the world, and data quantity processed there isincreasing explosively. Further, importance of data treated in computersystems rises, and high reliability is required for keeping data, and itbecomes social duty of an information system to prevent loss of dataheld in it by any kind of disaster.

In such a system, to ensure reliability of data, a storage itself ismultiplied. Data outputted from a processing host computer is not onlystored into a storage directly coupled to the host computer, but alsocopied to another storage via the directly coupled storage.

In the following, a storage directly coupled to a host computer iscalled a direct-coupled storage, and a storage that receives data notdirectly from the host computer but through the direct-coupled storageis called a remote storage.

Generally, a method of copying data to a remote storage through adirect-coupled storage is called remote copy, and applied to aninformation system that requires high reliability. According to thisremote copy technique, even when a failure occurs in a storage so thatthe storage falls into an inoperable state, system operation can becontinued using data of another storage.

When especially high reliability is required, it is possible to employ amethod in which a multitude of remote storages are concatenated, anddata is copied sequentially to the concatenated remote storages toincrease multiplicity (redundancy) of data and to increase reliability.

For example, in the case of an apparatus for cascading and storing data,which is disclosed in Published Japanese Translation No. 2002-542526 ofInternational Application (Patent Document 1), data is processed in aproduction site with a host computer and written into a direct-coupledstorage and then, redundant data store is transparently provided to twoor more remote storage. When a first remote storage receives data fromthe production site, the first remote storage transfers the data to asecond remote storage located in a remoter place. At that time, thefirst remote storage holds a copy progress status. When data copyoperation to the second remote storage is completed, the first remotestorage reports the completion to the direct-coupled storage in theproduction site.

Further, to enhance integrity against disaster such as an earthquake, itis favorable that remote storages are located at remoter places as faras possible. However, remote copy to a remote place takes time in datatransfer. To solve this problem, there is a method in which, at the timeof data update processing from a host computer, data transfer to remotestorages is performed asynchronously with transfer (host transfer) fromthe host computer to a direct-coupled storage, to realize efficientremote copy between a plurality of storage subsystems, as disclosed, forexample, in Japanese Patent Application Laid-Open No. 2002-334049(Patent Document 2).

According to the technique disclosed in Patent Document 2, at a point oftime when data transferred from the host computer is stored in aninternal buffer of the direct-coupled storage, completion of receptionis acknowledged to the host computer. And, thereafter, the host computermonitors the utilization factor of the internal buffer of thedirect-coupled storage to adjust data update intervals.

Further, in the case where data is inherited at a point of time when afailure occurs in a storage, it is necessary to ensure consistency ofdata between multiplied storages. As a technique of establishingconsistency of data, there is known a technique in which consistency ofdata contents is ensured as follows. Namely, a pair of volumesconsisting of a volume (which stores data) of a direct-coupled storageand a volume (as the copy destination of the data mentioned) of a remotestorage is defined, and a set of pairs of volumes are managed generallyas a group, in order to maintain the order of data update, as disclosed,for example, in Japanese Patent Application Laid-Open No. 2002-189570.

The technique disclosed in Patent Document 3 is a duplication method torecover a volume copy quickly within the group when an event thattemporarily stops copying, owing to maintenance or disaster. Accordingto the present technique, a data center in a remote place can take overprocessing at the time when an information system suffers from disaster.

SUMMARY OF THE INVENTION

The techniques disclosed in the above-mentioned Patent Documents 1 to 3can realize efficient remote copy between a direct-coupled storage andremote storages and realize multiple data.

Recently, quantity of treated data is increasing, and, in some cases, aplurality of direct-coupled storages is connected to a host computer,and each direct-coupled storage is connected with remote storages. Inthe case where data is transferred from one host computer to a pluralityof direct-coupled storages, there is a desire to generally collectvarious kinds of information, such as remote copy status information, oneach of the direct-coupled storages and each of the remote storagessequentially concatenated from a direct-coupled storage. This is desiredfor the host computer to perform processing corresponding to thecollected information, for example, the remote copy status.

In the technique disclosed in Patent Document 1, a storage as a copysource obtains a progress status in the course of remote copy. However,Patent Document 1 does not disclose any arrangement for providing theabove-mentioned information to the host computer. Further, PatentDocuments 2 and 3 describe techniques of efficient remote copy only, anddoes not describe acquisition of remote copy status information or thelike of a remote storage.

Thus, in these techniques, a host computer can not know various kinds ofinformation such as remote copy progress status in a remote storage.

The present invention solves the above-described problems, and it is anobject of the present invention that a host computer obtains statusinformation and the like of a remote storage that is not directlycoupled to the host computer, through a simple interface.

To attain the above object, a storage subsystem according to the presentinvention is a storage subsystem in a computer system in which aplurality of storage subsystems are sequentially concatenated to a hostcomputer and remote copy is performed between the above-mentionedplurality of storage subsystems, and the storage subsystem comprises ameans which judges its own concatenation position, a means which sendsreceived status information acquisition command, and a means which sendsstatus information.

In detail, the storage subsystem comprises:

an interface which receives status information acquisition command andwhich sends status information from and to a storage subsystem(hereinafter, referred to as an upstream storage subsystem) that islocated on a nearer side of the storage subsystem in question seen fromthe host computer and connected to the storage subsystem in question;

an outgoing status information storage unit which stores said statusinformation (hereinafter, referred to outgoing status information) to besent to said upstream storage subsystem;

a target storage subsystem judgment unit which judges whether a targetstorage subsystem (meaning a storage subsystem from which said statusinformation is to be acquired) stored in the status informationacquisition command received through said interface is the storagesubsystem in question;

a command downstream sending unit which sends said status informationacquisition command to a storage subsystem (hereinafter, referred to asa downstream storage subsystem) that is located on a farther side of thestorage subsystem in question seen from the host computer and connectedto the storage subsystem in question, when said target storage subsystemjudgment unit judges that the storage subsystem in question is not saidtarget storage subsystem from which said status information is to beacquired;

a self status information acquisition unit which acquires the statusinformation of the storage subsystem in question and which stores theacquired status information as said outgoing status information intosaid outgoing status information storage unit, when said target storagesubsystem judgment unit judges that the storage subsystem in question issaid target storage subsystem from which said status information is tobe acquired; and

a downstream status information acquisition unit which receives thestatus information from said downstream storage subsystem and whichstores the received status information as said outgoing statusinformation into said outgoing status information storage unit; and

after said self status information acquisition unit or said downstreamstatus information acquisition unit stores said outgoing statusinformation into said outgoing status information storage unit, saidinterface sends said status information stored.

According to the present invention, using a simple interface, a hostcomputer can acquire remote copy status information and the like ofstorage subsystems that are located at remote places without beingdirectly coupled to the host computer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a system configuration of a storagesystem of an embodiment of the present invention;

FIG. 2 is a block diagram showing a functional configuration of a hostcomputer in an embodiment of the present invention;

FIG. 3 is a block diagram showing a functional configuration of astorage controller in an embodiment of the present invention;

FIG. 4 is a block diagram showing a hardware configuration of a hostcomputer in an embodiment of the present invention;

FIG. 5 is a block diagram showing a hardware configuration of a storagecontroller in an embodiment of the present invention;

FIG. 6 is a diagram for explaining information held as storage siteinformation in an embodiment of the present invention;

FIG. 7 is a diagram for explaining sequence information in an embodimentof the present invention;

FIG. 8 is a diagram for explaining sequence status information in anembodiment of the present invention;

FIG. 9 is a diagram for explaining a status information acquisitioncommand in an embodiment of the present invention;

FIG. 10 is a diagram for explaining a status information response in anembodiment of the present invention;

FIG. 11 is a flowchart showing status information request processingperformed in a host computer in an embodiment of the present invention;

FIG. 12 is a flowchart showing processing performed in a host computerwhen status information is acquired in an embodiment of the presentinvention;

FIG. 13 is a flowchart showing processing performed in a storagesubsystem when a status information acquisition command includingSpecific-Newest Command is received in an embodiment of the presentinvention;

FIG. 14 is a flowchart showing processing performed in a storagesubsystem when a status information acquisition command includingSequence-Newest Command is received in an embodiment of the presentinvention;

FIG. 15 is a flowchart showing processing performed in a storagesubsystem when a status information acquisition command includingRegular-lnterval-Sequence-Status Acquisition Command is received in anembodiment of the present invention; and

FIG. 16 is a flowchart showing adjustment processing performed in aremote copy adjustment unit in an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Now, embodiments of the present invention will be described referring todrawings.

FIG. 1 is a block diagram showing a system configuration of the presentembodiment.

A storage system of the present embodiment comprises a host computer100, storage subsystems 1300A1, 1300B1, 1300C1, 1300A2, 1300B2 and1300C2. Further, each storage subsystem comprises a storage controller1400A1, 1400B1, 1400C1, 1400A2, 1400B2 or 1400C2, and a disk array1500A1, 1500B1, 1500C1, 1500A2, 1500B2 or 1500C2.

The host computer 100 performs various kinds of processing, stores datainto the storage subsystems belonging to the storage system, and managesall the storage subsystems belonging to the storage system.

In the present embodiment, the storage subsystems 1300A1 and 1300A2 aredirectly coupled to the host computer 100. In the present embodiment,this example having two storage subsystems directly coupled to the hostcomputer 100 is described, although the number of storage subsystemscoupled to a host computer is not limited to two. Hereinafter, thestorage subsystems directly coupled to the host computer are calleddirect-coupled storage subsystems, to distinguish them from the otherstorage subsystems.

Further, the storage subsystems 1300B1 and 1300B2 are storage subsystemsconnected respectively to the direct-coupled storage subsystems 1300A1and 1300A2. The storage subsystems 1300C1 and 1300C2 are storagesubsystems connected respectively to the storage subsystems 1300B1 and1300B2. These storage subsystems that are not directly coupled to thehost computer are generally called remote storage subsystems. The remotesubsystems are connected such that one or more storage subsystems areconnected in series to one direct-coupled storage subsystem. The numberof remote storage subsystems connected in series is not limited.Further, it is possible that a direct-coupled storage subsystem is notconnected with a remote storage subsystem.

Data outputted from the host computer 100 to a direct-coupled storagesubsystem 1300A1 or 1300A2 is remotely copied to storage subsystems1300B1 and 1300C1 or 1300B2 and 1300C2 connected in series. When remotecopy is performed from a direct-coupled storage subsystem tosequentially-concatenated storage subsystems, a set of the concatenatedstorage subsystems is called a sequence. Further, among storagesubsystems in a sequence, a storage subsystem on the nearer side seenfrom the host computer is called upstream one and a storage subsystem onthe farther side seen from the host computer is called downstream one.

In the present embodiment, the host computer can obtain information on ahalfway status of remote copy. Thus, the present embodiment is describedtaking the example where the host computer obtains status information ofremote copy, although the present invention is not limited to this. Forexample, a configuration similar to the present embodiment can obtainconfiguration information and log information of a remote storagesubsystem.

Further, the storage subsystems 1300A1, 1300B1 and 1300C1 in a sequenceare located at different data centers respectively. Each data center islocated at a remote place, and connected with one another through anetwork of fiber channels, for example. Also the other sequence isarranged similarly.

When it is not necessary to distinguish an individual storage subsystem,an individual storage controller or an individual disk array, arepresentative expression such as “a storage subsystem 1300”, “a storagecontroller 1400” or “a disk array 1500” is used in this description.Further, when it is not necessary to distinguish between thedirect-coupled storage subsystems, “a direct-coupled storage subsystem1300A” is used as a representative expression.

Next, functional configurations of the host computer 100 and a storagesubsystem 1300 will be described.

FIG. 2 is a block diagram showing a functional configuration of the hostcomputer 100.

As shown in the figure, the host computer 100 comprises a remote copymonitoring unit 101, a remote copy adjustment unit 102, a concatenationinformation acquisition unit 103, a sequence information acquisitionunit 104, storage site information 500, sequence information 600, andacquired status information 300.

The concatenation information acquisition unit 103 receives information(inputted by an administrator) on a concatenation configuration ofstorage subsystems 1300, and generates and holds the storage siteinformation 500.

An example held as the storage site information 500 is shown in FIG. 6.As shown in the figure, the storage site information 500 includes: aconcatenated storage site number 510 showing the number of storagesubsystems 1300 concatenated in the sequence; a storage site identifier530, i.e., information specifying each storage subsystem 1300 belongingto the sequence; and concatenation order information 520 indicating theconcatenation order of the storage subsystems 1300 in the sequence.

In the present embodiment, consecutive natural numbers (in which asmaller number means an upstream storage subsystem 1300) are held as theconcatenation order information 520. Namely, “1” is held for thedirect-coupled storage subsystem 1300A1, “2” for the remote storagesubsystem 1300B1 connected to the direct-coupled storage subsystem1300A1, and “3” for the remote storage subsystem 1300C1 connected to theremote storage subsystem 1300B1. According to the concatenation orderinformation, the concatenation configuration of the storage subsystems1300 in each sequence can be grasped.

The sequence information acquisition unit 104 receives information(inputted by the administrator) on a concatenation configuration of adirect-coupled storage subsystem 1300A, and generates and holds thesequence information 600.

An example of the sequence information 600 is shown in FIG. 7. As shownin the figure, the sequence information 600 includes: a storagesubsystem number 610 showing the number of direct-coupled storagesubsystems 1300A concatenated to the host computer; a storage subsystemidentifier 630, i.e., information specifying each direct-coupled storagesubsystem 1300A; and connection order information 620 indicating theorder of connection of the direct-coupled storage subsystems 1300A tothe host computer. Referring to the sequence information 600, it ispossible to know the storage subsystems 1300A directly coupled to thehost computer.

The remote copy monitoring unit 101 obtains status information of allthe storage subsystems 1300 in the storage system, through thedirect-coupled storage subsystems 1300A, and monitors remote copy ineach sequence, based on the status information.

In detail, when the remote copy monitoring unit 101 receives aninstruction from a user through the below-mentioned input device 140 toacquire status information, then, the remote copy monitoring unit 101generates a status information acquisition command 800 described belowto acquire status information, and sends the generated statusinformation acquisition command 800 to a direct-coupled storagesubsystem 1300A. In the present embodiment, the remote copy monitoringunit 101 receives the following designation from the user, namely,designation of the type of status information to acquire, and thestorage subsystem and the pair of volumes as the target from whichstatus information is to acquire, and, when the below-mentioned intervalprocessing is required, designation of the time interval.

Further, when status information is received from a direct-coupledstorage subsystem 1300A, the received status information is held as theacquired status information 300. The acquired status informationconsists of the below-described status information acquisition command800 and the status information sent from the direct-coupled storagesubsystem 1300A.

The acquired status information 300 is displayed on the below-mentioneddisplay device 150 by a display control unit not shown, or the like.From the displayed contents, the user can know the status information ofthe desired storage subsystem 1300.

Now, will be described a status information acquisition command 800 thatis generated by the remote copy monitoring unit 101 to acquire statusinformation of a storage subsystem belonging to the storage systemmanaged by the host computer 100 that owns the remote copy monitoringunit 101 in question.

FIG. 9 shows an example of a status information acquisition command 800.

As shown in the figure, a status information acquisition command 800includes: a command identifier storage part 860; a remote copy statusacquisition command type storage part 810; an acquisition targetidentifier storage part 820; a pair identifier storage part 830; atype-of-information-to-acquire storage part 840; and an interval storagepart 850.

The command identifier storage part 860 stores a command identifier asinformation for identifying a command. A command identifier isautomatically given when a status information acquisition command 800 isgenerated, to uniquely identify each status information acquisitioncommand. When status information is returned in response to a statusinformation acquisition command 800, a storage subsystem 1300 that hasreceived the status information acquisition command 800 gives thecommand identifier to the status information to be returned. Receivingstatus information from a direct-coupled storage subsystem 1300A, theremote copy monitoring unit 101 can judge for which status informationacquisition command 800, the received status information is received inreturn.

The remote copy status acquisition command type storage part 810 storesa command type corresponding to a type of remote copy status to acquire.As a command type, the present embodiment prepares five types dependingon: the target from which status information is to be acquired; whetherstatus information is the newest or already-held information; andwhether status information is to be accumulated at given time intervals.

Namely, the five command types are: (1) Specific-Newest Command, whichgives an instruction of acquiring newest status information on aspecific storage subsystem 1300; (2) Specific-Existing Command, whichgives an instruction of acquiring status information that relates to aspecific storage subsystem 1300 and that has been already acquired andis held in a direct-coupled storage subsystem 1300A; (3) Sequence-NewestCommand, which gives an instruction of acquiring newest statusinformation on all the storage subsystems 1300 belonging to a specificsequence; (4) Sequence-Existing Command, which gives an instruction ofacquiring status information that relates to all the storage subsystems1300 belonging to a specific sequence and that has been already acquiredand held in the direct-coupled storage subsystem 1300A of the sequencein question; and (5) Regular-lnterval-Sequence-Status AcquisitionCommand, which gives an instruction of accumulating the newest statusinformation on all the storage subsystems 1300 belonging to a specificsequence at given time intervals into the direct-coupled storagesubsystem 1300A. One of these types is stored in the remote copy statusacquisition command type storage part 810.

Receiving a status information acquisition command 800, a storagesubsystem 1300 performs processing which acquires status information,according to the command type stored in the remote copy statusacquisition command type storage part 810 of the received statusinformation acquisition command 800. Although the present inventiontakes an example where the above-described five types are prepared,command types are not limited to these. For example, there may beprepared a command type for acquiring status information on a specificstorage subsystem 1300 at given intervals.

The acquisition target identifier storage part 820 stores informationthat specifies a storage subsystem 1300 or a sequence from which statusinformation is acquired. In detail, referring to the storage siteinformation 500, the storage site identifier 530 of the storagesubsystem 1300 from which status information is acquired, theconcatenation order information 520 corresponding to that storage siteidentifier 530, and the concatenated storage site number 510 are stored.Meaning of information stored in this storage part 820 differs dependingon the command type stored in the remote copy status acquisition commandtype storage part 810.

For example, in the case where Specific-Newest Command orSpecific-Existing Command, which gives an instruction of acquiringstatus information on a specific storage subsystem 1300, is stored, itis judged that the storage subsystem 1300 stored in the acquisitiontarget identifier storage part 820 is the storage subsystem 1300 fromwhich status information is acquired according to the status informationacquisition command 800.

On the other hand, in the case where Sequence-Newest Command,Sequence-Existing Command or Regular-Interval-Sequence-StatusAcquisition Command, which gives an instruction of acquiring statusinformation of all the storage subsystems 1300 of a sequence, is stored,the acquisition target identifier storage part 820 stores thedirect-coupled storage subsystem 1300A belonging to the sequence as thetarget which acquires status information. Thus, it is judged that asequence whose top is the stored direct-coupled storage subsystem 1300is the sequence as the target which acquires status informationaccording to the status information acquisition command 800.

The type-of-information-to-acquire storage part 840 stores informationthat specifies which type of status information is to be acquired. Thepresent embodiment prepares three types: Copy Status, which indicates aconcordance rate of data between a pair of volumes in remote copy;Transfer Rate, which indicates a data transfer rate in remote copy; andCache Usage, which indicates a usage rate of the cache of a storagesubsystem. One or more of these types are designated.

The pair identifier storage part 830 stores information specifying apair of volumes whose status information of remote copy is to acquire.This information is stored when a command type stored in the remote copystatus acquisition command type storage part 810 is Specific-NewestCommand or Specific-Existing Command, and the information stored in thetype-of-information-to-acquire storage part 840 (i.e., the informationthat specifies which type of status information is to be acquired) isCopy Status or Transfer Rate.

The interval storage part 850 stores information relating to intervalprocessing. Here, in the present embodiment, “interval processing” meansprocessing of acquiring status information of all the storage subsystems1300 of a sequence to update information of the below-mentioned sequencestatus information storage unit 700 held by the direct-coupled storagesubsystem 1300A. Thus, the information relating to the intervalprocessing is relevant only when the command type stored in the remotecopy status acquisition command type storage part 810 isRegular-lnterval-Sequence-Status Acquisition Command. In the presentembodiment, in the case where the interval processing is performed, theinterval storage part 850 stores the time interval of the intervalprocessing. In the case of sending an instruction of stopping intervalprocessing, a predetermined data, for example “0” is stored into theinterval storage part 850.

According to an instruction received from a user through thebelow-mentioned input device 140, the remote copy adjustment unit 102compares status information between sequences or storage subsystems1300, and outputs a comparison result to the below-mentioned outputdevice 150, for example. Based on the contents of the output, the usercan change the below-mentioned intervals at which status information isacquired, break the remote copy processing itself, or detach a storagesubsystem 1300.

FIG. 4 shows a hardware configuration of the above-described hostcomputer 100.

As shown in the figure, the host computer 100 comprises a processor 110,a memory 120, a storage interface 130, an input device 140 and a displaydevice 150.

The above-described functions of the remote copy monitoring unit 101,the remote adjustment unit 102, the concatenation informationacquisition unit 103 and the sequence information acquisition unit 104are each realized when a program is stored in the memory 120 andexecuted by the processor 110. Further, the storage site information500, the sequence information 600 and the acquired status information300 are stored in the memory 120.

Next, a storage subsystem 1300 will be described. As shown in FIG. 1, astorage subsystem 1300 comprises a storage controller 1400 and a diskarray 1500. The disk array 1500 stores information received from thehost computer 100, includes volumes as a plurality of storage areas, andis managed in volumes.

The storage controller 1400 controls processing of storing information(received from the host computer) to the disk array 1500, remote copyprocessing destined to downstream storage subsystems connected to thestorage subsystem 1300 of the storage controller 1400 itself, processingof acquiring status information, and other processing.

FIG. 3 shows a functional configuration of a storage controller 1400.

As shown in the figure, a storage controller 1400 comprises an interfacecontrol unit 401, a concatenation position self judgment unit 402, astatus information acquisition unit 403, an interval processing unit 404and sequence status information 700.

The status information acquisition unit 403 continuously monitors theinside status of its own storage subsystem 1300 in the course of remotecopy, and holds a monitoring result as the sequence status information700.

For example, the status information acquisition unit 403 acquires statusinformation at given intervals, and uses the acquired status informationto update the sequence status information 700. Further, when the statusinformation acquisition unit 403 receives status information from adownstream storage subsystem 1300 than its own storage subsystem 1300,through the below-mentioned interface control unit 401, then, the statusinformation acquisition unit 403 adds a new entry to the sequence statusinformation 700 to store the status information.

Now, the sequence status information 700 will be described.

FIG. 8 shows an example of sequence status information 700. Here, by wayof example, FIG. 8 shows sequence status information 700 held by adirect-coupled storage subsystem 1300A.

As shown in the figure, sequence status information 700 includes: astorage site information storage part 710 which stores storage siteinformation that identifies two storage subsystems 1300 relating toremote copy; a volume identifier storage part 720 which stores volumeidentifiers of two disk arrays relating to remote copy; a statusinformation storage part 730 which stores status information; and aupdate time storage part 740 which stores the time when the statusinformation was updated. Further, the status information storage part730 includes: a copy status storage part 731 which stores a remote copyprogress; a transfer rate storage part 732 which stores a transfer rateof remote copy; and a cache usage storage part 733 which stores a usagerate of the cache memory.

The copy status storage part 731 may store copy status information suchas a duplex state in which a pair relation of a pair of volumes ismaintained, a suspended state in which a pair relation is suspended, orthe like.

Further, when the storage site includes two storage subsystems 1300 asin the case where data is copied from the storage subsystem 1300A1 tothe storage subsystem 1300B1 for example, the entries other than thecopy status and the transfer rate are held by both the storagesubsystems 1300 concerned, and the copy status and the transfer rate areheld by the storage subsystem on the side of the copy source.

When the concatenation position self judgment unit 402 receives aninstruction from the below-mentioned interface control unit 401, theconcatenation position self judgment unit 402 extracts information inthe acquisition target identifier storage part 820 to judge theconcatenation position of its own storage subsystem 1300 in thesequence.

In detail, the concatenation position self judgment unit 402 judges itsown concatenation position based on the concatenation order information520 and the concatenated storage site number 510 stored in associationwith the storage site identifier 530 coincident with the storage siteidentifier 530 that is held in advance in the concatenation positionself judgment unit 402 itself and that specifies its own storagesubsystem 1300, among the storage site identifiers 530 stored in theacquisition target identifier storage part 820.

For example, when the concatenated storage site number 510 is “1” andits own concatenation order information 520 is “1”, then, theconcatenation position self judgment unit 402 judges that its ownstorage subsystem 1300 is directly coupled to the host computer andlocated at the end position. Or, in the case where the number of theconcatenation stored in the concatenated storage site number 510 is “6”,and the concatenation order shown by its concatenation order information520 is “1”, then, it is judged that its own storage subsystem 1300 isdirectly coupled to the host computer and is not located at the endposition. Or, when the concatenation order is “6”, it is judged that itsown storage subsystem 1300 is located at the end position of thesequence.

The interface control unit 401 receives a status information acquisitioncommand 800 from the host computer 100 or the upstream storage subsystem1300 to its own storage subsystem 1300, and interprets and processes thereceived status information acquisition command 800. Further, when astatus information response 900, which stores status information, fromthe downstream storage subsystem 1300 to its own storage subsystem 1300,then, the interface control unit 401 sends the received statusinformation response 900 to the upstream storage subsystem 1300 or thehost computer 100.

Here, a status information response 900 returned from a storagesubsystem 1300 will be described.

FIG. 10 shows an example of a status information response 900. As shownin the figure, a status information response 900 includes a commandidentifier storage part 910, a status information storage part 920, acommand type storage part 930, and an update time storage part 940.

When a status information acquisition command 800 is received, theinterface control unit 401 extracts the above-mentioned command typestored in the remote copy status acquisition command type storage part810 out of the status information acquisition command 800, to identifythe command type.

In the case where the command type stored in the remote copy statusacquisition command type storage part 810 is the above-mentionedSpecific-Newest Command, the identifier stored in the acquisition targetidentifier storage part 820 is extracted, to judge whether the storagesubsystem 1300 specified as the target of acquisition is its own storagesubsystem 1300.

When its own storage subsystem 1300 is specified, a status informationresponse 900 is generated. Out of the information held as the sequencestatus information 700 by the status information acquisition unit 403,the status information designated by the received status informationacquisition command 800 and the update time corresponding to the statusinformation are received and stored respectively into the statusinformation storage part 920 and the update time storage part 940 of thegenerated status information response 900. Further, the commandidentifier and the command type stored respectively in the commandidentifier storage part 860 and the remote copy status acquisitioncommand type storage part 810 are stored into the command identifierstorage part 910 and the command type storage part 930 of the statusinformation response 900. Then, the status information response 900 issent to the upstream storage subsystem 1300 connected to the storagesubsystem 1300 in question. Here, in the case where the storagesubsystem 1300 in question is a direct-coupled storage subsystem 1300A,the status information response 900 is sent to the host computer.

In the case where the storage subsystem 1300 designated as the target ofacquisition is not its own storage subsystem 1300, then, the interfacecontrol unit 401 sends the status information acquisition command 800 tothe downstream storage subsystem 1300 connected to its own storagesubsystem 1300.

In the case where the storage subsystem 1300 to which the interfacecontrol unit 401 belongs (i.e., its own storage subsystem 1300) is anend (i.e., the lowest) storage subsystem 1300, and the storage subsystem1300 designated as the target of acquisition is not its own storagesubsystem 1300, then, the received status information acquisitioncommand 800 is discarded.

In the case where the command type stored in the remote copy statusacquisition command type storage part 810 is the above-mentionedSpecific-Existing Command, the interface control unit 401 extracts theidentifier stored in the acquisition target identifier storage part 820and the identifier stored in the pair identifier storage part 830, toconfirm whether the status information of the storage subsystem 1300 andthe pair of volumes designated as the target of acquisition is stored inthe sequence status information 700 held by the storage subsystem 1300of its own.

In the case where the sequence status information 700 stores the statusinformation in question, a status information response 900 is generated.And, according to the information type stored in thetype-of-information-to-acquire storage part 840, the relevant statusinformation and the update time in the sequence status information 700are stored into the status information storage part 920 and the updatetime storage part 940 of the generated status information response 900.Further, the command identifier and the command type stored respectivelyin the command identifier storage part 860 and the remote copy statusacquisition command type storage part 810 of the received statusinformation acquisition command 800 are stored respectively into thecommand identifier storage part 910 and the command type storage part930 of the status information response 900. Then, the status informationresponse 900 is sent to the host computer 100.

In the case where the status information of the storage subsystem 1300and the pair of volumes designated as the target of acquisition is notstored in the sequence status information 700 held by the storagesubsystem 1300 of its own, the processing of the above-described casewhere Specific-Newest Command is received is performed.

In the case where no status information of the storage subsystem 1300specified as the target of acquisition is stored in the sequence statusinformation 700, the interface control unit 401 discards the statusinformation acquisition command 800.

In the case where the command type stored in the remote copy statusacquisition command type storage part 810 is the above-mentionedSequence-Newest Command, the interface control unit 401 confirms theinformation stored in the acquisition target identifier storage part 820to specify the target of acquisition. In the case where the storagesubsystem 1300 to which the interface control unit 401 itself belongs(i.e., its own storage subsystem) is a direct-coupled storage subsystem1300A and the information stored in the acquisition target identifierstorage part 820 indicates its own storage subsystem 1300A, then, theinterface control unit 401 sends the status information acquisitioncommand 800 to the downstream storage subsystem 1300 connected to itsown storage subsystem 1300A.

In the case where the storage subsystem 1300 of its own is not adirect-coupled storage subsystem 1300A, the interface control unit 401sends the status information acquisition command 800 to the downstreamstorage subsystem 1300 connected to the storage subsystem 1300 of itsown, unless the concatenation position self judgment unit 402 judgesthat the storage subsystem 1300 of its own is an end storage subsystem1300.

In the case where the storage subsystem 1300 of its own is judged to bean end storage subsystem 1300, a status information response 900 isgenerated and sent to the upstream storage subsystem 1300 connected tothe storage subsystem 1300 of its own. Here, information stored in eachstorage part of the status information response is same as theabove-described case of Specific-Newest Command.

In the case where the command type stored in the remote copy statusacquisition command type storage part 810 is the above-mentionedSequence-Existing Command, then, the interface control unit 401 confirmsthe information stored in the acquisition target identifier storage part820 to specify the target of acquisition. In the case where the storagesubsystem 1300 to which the interface control unit 401 itself belongs(i.e., its own storage subsystem) is a direct-coupled storage subsystem1300A and the information stored in the acquisition target identifierstorage part 820 indicates its own storage subsystem 1300A, theinterface control unit 401 stores the status information that is held byits own storage subsystem 1300A and that relates to all the storagesubsystems 1300 of the sequence into the status information response900, to send the status information response 900 to the host computer100.

At that time, the command identifier storage part 910 and the commandtype storage part 930 store the corresponding information stored in thereceived status information acquisition command 800. And, the statusinformation storage part 920 and the update time storage part 940 storethe corresponding information of all the storage subsystems 1300 and thepairs of volumes stored in the sequence status information 700 held bythe storage subsystem 1300A of its own.

Further, in the case where the command type stored in the remote copystatus acquisition command type storage part 810 isRegular-Interval-Sequence-Status Acquisition Command, and its ownstorage subsystem 1300 is judged to be an end storage subsystem 1300,then, the interface control unit 401 extracts the information of theinterval storage part 850 of the received status information acquisitioncommand 800, and delivers the extracted information to thebelow-mentioned interval processing unit 404.

In the present embodiment, in the case where the interval storage part850 stores the time interval at which the interval processing isperformed, it means that status information is acquired at the timeintervals, each interval having the value stored in the interval storagepart 850. On the other hand, in the case where the interval storage part850 stores “0”, it means an instruction of stopping the intervalprocessing.

Further, the interface control unit 401 receives a status informationresponse 900 from the downstream storage subsystem 1300.

First, the interface control unit 401 makes the status informationacquisition unit 403 store the status information of the received statusinformation response 900 into the sequence status information storageunit 700 of its own storage subsystem 1300. Then, referring to thecommand type storage part 930 of the received status information 900,the interface control unit 401 judges the type of the command accordingto which the status information response 900 in question has been sent.

In the case where it is judged that the status information response 900has been sent according to Specific-Newest Command or Specific-ExistingCommand and the storage subsystem of its own is not a direct-coupledstorage subsystem 1300A, then, the interface control unit 401 extractsagain the status information stored in the received status informationresponse 900 from the status information stored in the sequence statusinformation 700, and composes a status information response 900 to sendthe composed status information response 900 as it is to the upstreamstorage subsystem 1300 connected to its own storage subsystem 1300. Whenits own storage subsystem 1300 is a direct-coupled storage subsystem1300A, the composed status information 900 is sent to the host computer100.

Or, the following arrangement may be employed here. Namely, when it isjudged that the status information response 900 has been sent accordingto Specific-Newest Command or Specific-Existing Command, then, thestatus information response 900 received from the downstream storagesubsystem 1300 is sent as it is to the upstream storage subsystem 1300or to the host computer 100.

Further, when it is judged that the received status information response900 has been sent according to Sequence-Newest Command,Sequence-Existing Command, or Regular-Interval-Sequence-StatusAcquisition Command, and its own storage subsystem 1300 is not adirect-coupled storage subsystem 1300A, then, using its own statusinformation and the status information of all the downstream storagesubsystems stored in the sequence status information 700, the statusinformation and the update time designated in the status informationacquisition command 800 are extracted to compose a status informationresponse 900. Then, the composed status information response 900 is sentto the upstream storage subsystem 1300 connected to its own storagesubsystem 1300. On the other hand, when its own storage subsystem 1300is a direct-coupled storage subsystem 1300A, the composed statusinformation response 900 is sent to the host computer 100.

The interface control unit 401 makes the status information acquisitionunit 403 add the status information of the downstream storage subsystems1300 stored in the received status information response 900 to thesequence status information 700, and sends the received statusinformation response 900 to the upstream storage subsystem 1300connected to its own storage subsystem 1300. In the case ofSequence-Newest Command and when its own storage subsystem is adirect-coupled storage subsystem 1300A, then, the received statusinformation response 900 is sent to the host computer 100.

The interval processing unit 404 holds a timer for measuring time. Whenthe information on the time interval for the interval processing isreceived from the interface control unit 401, the interval processingunit 404 starts to measure time anew. When time of the received timeinterval elapses, the interval processing unit. 404 instructs theinterface control unit 401 to perform the processing. On the other hand,when, as the information on the interval processing, “0” is receivedfrom the interface control unit 401, then, the interval processing unit404 stops the time measurement using the timer, to stop the intervalprocessing.

FIG. 5 shows a hardware configuration of the above-described storagecontroller 1400 of a storage subsystem 1300.

As shown in the figure, the storage controller 1400 comprises aprocessor 410, a memory 420, a cache memory 430, a host interface 440and a storage interface 450.

The above-described functions of the interface control unit 401, theconcatenation position self judgment unit 402, the status informationacquisition unit 403 and the interval processing unit 404 are eachrealized when a program is stored in the memory 420 and executed by theprocessor 410. Further, the sequence status information 700 is stored inthe memory 420.

Next, will be described processing performed when the host computer 100requests status information from a storage subsystem 1300.

FIG. 11 is a flowchart for explaining the processing performed when thehost computer 100 requests status information.

When the remote copy monitoring unit 101 receives an instruction from auser through the input device 140, to acquire status information (Step1101), then, the remote copy monitoring unit 101 generates a statusinformation acquisition command 800 according to the receivedinstruction.

First, the remote copy status acquisition command type and the type ofthe status information to acquire, shown in the instruction receivedfrom the user, are stored into the remote copy status acquisitioncommand type storage part 810 and the type-of-information-to-acquirestorage part 840, respectively (Step 1102).

Next, from the storage site information 500, the remote copy monitoringunit 101 acquires the concatenation information on the storage subsystem1300 whose status information is to acquire according to the instructionreceived from the user, and stores the acquired information into theacquisition target identifier storage part 820. The remote copymonitoring unit 101 also stores the pair of volumes which acquireaccording to the instruction received from the user into the pairidentifier storage part 830 (Step 1103)

Then, it is judged whether designation of the time interval of theinterval processing or stopping of the interval processing has beenreceived (Step 1104). In the case where such designation has beenreceived, the received time interval of the interval processing or “0”is stored into the interval storage part 850 (Step 1105).

Next, the remote copy monitoring unit 101 stores a command identifier,which is automatically given to uniquely identifying the statusinformation acquisition command 800, into the command identifier storagepart 860 (Step 1106).

Last, the status information acquisition command 800 generated is sendto a direct-coupled storage subsystem 1300A connected to the hostcomputer 100 itself, and the generated status information acquisitioncommand 800 is stored into the acquired status information 300 (Step1107).

Next, will be described processing performed when the host computer 100receives status information from a direct-coupled storage subsystem1300.

FIG. 12 shows a processing flow for explaining the processing performedwhen the host computer 100 receives status information.

When a status information response 900 is received from a direct-coupledstorage subsystem 1300A (Step 1201), the remote copy monitoring unit 101extracts a command identifier from the command identifier storage part910 of the received status information response 900, and compares theextracted command identifier with command identifiers of statusinformation acquisition commands 800 sent from the remote copymonitoring unit 101 and stored in the acquired status information 300(Step 1202).

When there is found a command identification that agrees with theextracted command identifier, then, the remote copy monitoring unit 101holds the received status information response 900 as the acquiredstatus information 300, i.e., as a reply to the status informationacquisition command 800 of the found command identification (Step 1203).

Where there is not found a command identifier that agrees with theextracted command identification, then, the remote copy monitoring unit101 outputs “error” to the display device 150 (Step 1204).

Next, will be described processing performed by the storage controller1400 of a storage subsystem 1300 when a status information acquisitioncommand 800 is received.

FIG. 13 shows a processing flow for explaining the processing performedwhen Specific-Newest Command is stored in the remote copy statusacquisition command type storage part 810 of the received statusinformation acquisition command 800.

When the interface control unit 401 receives the status informationacquisition command 800 (Step 3001), the interface control unit 401refers to the acquisition target identifier storage part 820 to judgewhether its own storage subsystem 1300 is the storage subsystem 1300 asthe target of acquisition (Step 3002).

In the case where its own storage subsystem 1300 is the target ofacquisition, then, the interface control unit 401 acquires thedesignated status information from the sequence status information 700held in the status information acquisition unit 403 to compose a statusinformation response 900 (Step 3003).

Next, the interface control unit 401 makes the concatenation positionself judgment unit 402 judge the concatenation position of its ownstorage subsystem (Step 3004). When its own storage subsystem is judgedto be a direct-coupled storage subsystem 1300A, the interface controlunit 401 sends the status information response 900 to the host computer100 (Step 3005). When it is judged that its own storage subsystem is nota direct-coupled storage subsystem 1300A, then, the interface controlunit 401 sends the status information response 900 to the upstreamstorage subsystem 1300 connected to its own storage subsystem (Step3006).

Next, in the case where it is judged that its own storage subsystem isnot the storage subsystem 1300 as the target of acquisition in Step3002, then, the interface control unit 401 sends the status informationacquisition command 800 to the downstream storage subsystem 1300connected to its own storage subsystem 1300, to await return of a statusinformation response 900 (Step 3007).

When a status information response 900 is received from the storagesubsystem 1300 connected to its own storage subsystem, then, theinterface control unit 401 adds the received status information to thesequence status information 700 (Step 3008), and composes a new statusinformation response 900 from the added status information (Step 3009),to proceeds to Step 3004.

In the case where Specific-Existing Command is stored in a statusinformation acquisition command 800, then, when a direct-coupled storagesubsystem 1300A receives the status information acquisition command 800,the status information of the designated storage subsystem 1300 isextracted from the sequence status information 700 held by thedirect-coupled storage subsystem 1300A itself, to send the extractedstatus information to the host computer 100. However, when thedirect-coupled storage subsystem 1300A does not hold the sequence statusinformation 700, then, the direct-coupled storage subsystem 1300Aperforms the processing of the above-described case where a statusinformation acquisition command 800 including Specific-Newest Command isreceived.

Next, will be described processing performed when Sequence-NewestCommand is stored in the remote copy status acquisition command typestorage part 810 of the received status information acquisition command800.

FIG. 14 shows a processing flow in the case of receiving the statusinformation acquisition command 800 that stores Sequence-Newest Command.

When the interface control unit 401 receives the status informationacquisition command 800 (Step 4001), the interface control unit 401makes the concatenation position self judgment unit 402 judge theconcatenation position of its own storage subsystem 1300 (Step 4002).

When it is judged that its own storage subsystem is a storage subsystem1300 connected at the end of the sequence, then, the designated statusinformation is acquired from the sequence status information 700 held bythe status information acquisition unit 403 to compose a statusinformation response 900 (Step 4003).

In Step 4002, when it is judged that its own storage subsystem is not astorage subsystem 1300 connected at the end of the sequence, then, theinterface control unit 401 sends the status information acquisitioncommand 800 to the downstream storage subsystem 1300 connected to itsown storage subsystem and awaits return of a status information response900 (Step 4004).

When a status information response 900 is received from the storagesubsystem 1300 on the downstream side of its own storage subsystem,then, the interface control unit 401 adds the received statusinformation to the sequence status information 700 (Step 4005). Further,using the information stored in the sequence status information 700, theinterface control unit 401 composes a new status information response900 based on the status information of its own and of all the storagesubsystems 1300 on the downstream side (Step 4006).

Next, the interface control unit 401 makes the concatenation positionself judgment unit 402 judge the concatenation position of its ownstorage subsystem 1300 (Step 4007). When it is judged that its ownstorage subsystem 1300 is a direct-coupled storage subsystem 1300A,then, the interface control unit 401 sends the status informationresponse 900 to the host computer 100 (Step 4008). On the other hand,when it is judge that its own storage subsystem 1300 is not adirect-coupled storage subsystem 1300A, then, the interface control unit401 sends the status information response 900 to the upstream storagesubsystem 1300 connected to its own storage subsystem 1300 (Step 4009).

In the case where Sequence-Existing Command is stored in a statusinformation acquisition command 800, then, when a direct-coupled storagesubsystem 1300A receives the status information acquisition command 800,the sequence status information 700 held by the direct-coupled storagesubsystem 1300A itself is sent to the host computer 100. However, whenthe direct-coupled storage subsystem 1300A does not hold the sequencestatus information 700, then, the direct-coupled storage subsystem 1300Aperforms the processing of the above-described case where a statusinformation acquisition command 800 including Sequence-Newest Command isreceived.

Next, will be described processing performed whenRegular-lnterval-Sequence-Status Acquisition Command is stored in theremote copy status acquisition command type storage part 810 of thereceived status information acquisition command 800.

FIG. 15 shows a processing flow in the case of receiving the statusinformation acquisition command 800 that storesRegular-lnterval-Sequence-Status Acquisition Command.

When the interface control unit 401 receives the status informationacquisition command 800 (Step 5001), the interface control unit 401makes the concatenation position self judgment unit 402 judge theconcatenation position of its own storage subsystem 1300 (Step 5002).

When it is judged that its own storage subsystem 1300 is a storagesubsystem 1300 connected at the end of the sequence, then, the interfacecontrol unit 401 extracts the time interval stored in the intervalstorage part 850 (Step 5003).

Here, when “0” is stored in the interval storage part 850, the interfacecontrol unit 401 makes the interval processing unit 404 reset the timer(Step 5004), and ends the processing.

When it is found in Step 5003 that a time interval other than “0” isstored, then, the interval control unit 401 makes the intervalprocessing unit 404 set the stored time interval into the timer (Step5005).

When the interface control unit 401 receives a notice from the intervalprocessing unit 404 to the effect that the interval set in the timer haselapsed, then, the interface control unit 401 acquires the designatedstatus information from the sequence status information 700 held by thestatus information acquisition unit 403 to compose a status informationresponse 900 (Step 5006).

Further, when it is judged in Step 5002 that its own storage subsystem1300 is not a storage subsystem 1300 connected to the end of thesequence, then, the interface control unit 401 sends the statusinformation acquisition command 800 to the downstream storage subsystem1300 connected to its own storage subsystem, and awaits return of astatus information response 900 (Step 5007).

When a status information response 900 is received from the downstreamstorage subsystem 1300 connected to its own storage subsystem 1300, theinterface control unit 401 adds the received status information to thesequence status information 700 (Step 5008). And, using the informationstored in the sequence status information 700, the interface controlunit 401 composes a new status information response 900 based on thestatus information of its own and of all the storage subsystems 1300 onthe downstream side (Step 5009).

Next, the interface control unit 401 makes the concatenation positionself judgment unit 402 judge the concatenation position of its ownstorage subsystem 1300 (Step 5010). When it is judged that its ownstorage subsystem 1300 is a direct-coupled storage subsystem. 1300A,then, the interface control unit 401 holds the status information storedin the status information response 900 (Step 5011). On the other hand,when it is judged that its own storage subsystem 1300 is not adirect-coupled storage subsystem 1300A, then, the status informationresponse 900 is sent to the upstream storage subsystem 1300 connected toits own storage subsystem 1300 (Step 5012).

Next, the interface control unit 401 makes the concatenation positionself judgment unit 402 judge the concatenation position of its ownstorage subsystem 1300 (Step 5013). When its own storage subsystem 1300is an end storage subsystem 1300, the processing flow returns to Step5008. On the other hand, when it is judged that its own storagesubsystem is not an end storage subsystem 1300, the processing flowreturns to Step 5008 to await receipt of a status information response900 from the downstream storage subsystem connected to its own storagesubsystem 1300.

Hereinabove, has been described the processing performed whenRegular-lnterval-Sequence-Status Acquisition Command is stored in thereceived status information acquisition command 800.

Next, will be described remote copy adjustment processing performed whenthe host computer 100 receives the status information of a plurality ofsequences connected to the host computer 100 itself.

FIG. 16 shows a flow of the adjustment processing by the remote copyadjustment unit 102.

When an instruction of adjustment is received from a user through theinput device 140, the remote copy adjustment unit 102 refers to theacquired status information 300 to extract data having the same statusinformation type and the same update time as ones stored in the statusinformation storage part 920 and the update time storage part 940 of areceived status information response 900, from the status information ofeach sequence (Step 6001).

Among the extracted data, the remote copy adjustment unit 102 extracts asequence having status information that indicates its remote copy loadis increasing. For example, in the case where the status informationtype stored in the type-of-information-to-acquire storage part isTransfer Rate, it is judged whether there is a sequence in which a valueof the transfer rate is less than a predetermined threshold of thetransfer rate. Or, in the case of Cache Usage, it is judged whetherthere is a sequence in which a value of the cache usage rate is morethan a predetermined threshold of the cache usage rate (Step 6002).

In the case where there is no sequence that satisfies the condition inStep 6002, then, the processing is ended without doing anything further.

In the case where there is a sequence that satisfies the condition inStep 6002, the remote copy adjustment unit 102 makes the display device150 display the relevant sequence (Step 6003). Here, a storage subsystem1300 having a lower transfer rate or a higher cache usage rate asdescribed above is possibly a storage subsystem 1300 whose remote copyload is increasing or whose performance is decreasing. Thus, the usercan cope with this by watching display on the display device 150 tofrequently perform remote copy supervisory control of the storagesubsystem in question, or by lengthening the time interval of a statusinformation acquisition command 800 that includesRegular-lnterval-Sequence-Status Acquisition Command to reduce a loadthat the processing of collecting status information gives on thestorage controller 1400, for example.

Here, in the case where there is prepared, for example, a command foracquiring the sequence information of all the sequences connected to thehost computer 100 in such a way that the status information is acquiredin the connection order stored in the sequence information 600, then,the remote copy adjustment unit 102 may change values of the connectionorder information 620 of the sequence information 600 of the sequence inquestion such that the status information of the sequence in question isacquired prior to the status information of the other sequences.

As described above, according to the storage system of the presentembodiment, the host computer 100 can collect status information of adesired storage subsystem or a pair of volumes through a simpleinterface, out of the storage subsystems 1300 of a sequence for whichremote copy is managed generally. Further, it is possible to generallyacquire the status information of all the storage subsystems 1300belonging to that sequence, through a simple interface.

Further, it is possible to find a storage subsystem for which the loadat remote copy is increasing and to notify a user of it to attractuser's attention.

Further, since status information acquired generally for each of aplurality of sequences is held and the held status information ispresented to a user, the user can know a sequence for which the load atremote copy is increasing. Based on the presented information, the usercan remove the degraded sequence from the general monitoring or canadjust remote copy for improving the status.

As described above, according to the present embodiment, the hostcomputer can request and collect the following status informationthrough a simple interface: namely, the remote copy status informationof a storage subsystem that is located at a remote place and notdirectly coupled to the host computer; the status information of all thestorage subsystems in a sequence; and the status of all the storagesubsystems of a plurality of sequences.

Further, according to the present embodiment, it is also possible toemploy similar method to acquire various kinds of information, such asconfiguration information and log information, of a storage subsystemthat is located at a remote place and not directly coupled to the hostcomputer.

1. A storage subsystem (hereinafter, referred to as the storagesubsystem in question) in a computer system in which a plurality ofstorage subsystems are sequentially concatenated to a host computer andremote copy is performed between said plurality of storage subsystems,wherein: said storage subsystem in question comprises: an interfacewhich receives status information acquisition command and which sendsstatus information from and to a storage subsystem (hereinafter,referred to as an upstream storage subsystem) that is located on anearer side of the storage subsystem in question seen from the hostcomputer and connected to the storage subsystem in question; an outgoingstatus information storage unit which stores said status information(hereinafter, referred to outgoing status information) to be sent tosaid upstream storage subsystem; a target storage subsystem judgmentunit which judges whether a target storage subsystem (meaning a storagesubsystem from which said status information is to be acquired) storedin the status information acquisition command received through saidinterface is the storage subsystem in question; a command downstreamsending unit which sends said status information acquisition command toa storage subsystem (hereinafter, referred to as a downstream storagesubsystem) that is located on a farther side of the storage subsystem inquestion seen from the host computer and connected to the storagesubsystem in question, when said target storage subsystem judgment unitjudges that the storage subsystem in question is not said target storagesubsystem from which said status information is to be acquired; a selfstatus information acquisition unit which acquires the statusinformation of the storage subsystem in question and which stores theacquired status information as said outgoing status information intosaid outgoing status information storage unit, when said target storagesubsystem judgment unit judges that the storage subsystem in question issaid target storage subsystem from which said status information is tobe acquired; and a downstream status information acquisition unit whichreceives the status information from said downstream storage subsystemand which stores the received status information as said outgoing statusinformation into said outgoing status information storage unit; andafter said self status information acquisition unit or said downstreamstatus information acquisition unit stores said outgoing statusinformation into said outgoing status information storage unit, saidinterface sends said status information stored.